第四部分 拓扑怎么选
11 50 V 的四种拓扑
接下来讲拓扑:怎么做这件事?上一场 Andy 讲了那些「砖」。
在 50 V 这一级,我们做了很久——50 V 砖式变换器做了三十多年。所以你有全桥、有 LLC、有混合开关电容、有 buck。把 50 V 降到 12 V、降到 6 V,路子很多,而且各有优劣。
全桥:基于变压器,因此天然适合做成模块;要把变压器损耗压下来,需要很多层 PCB。它是 PWM 控制,非常好控,所以稳压不是问题,输出电压可以完全稳压。但效率和功率密度都是中等。它在 12 V 好使,在 6 V 也好使,因为改一下变压器匝比就行,复杂度不高——本质上就是一颗带变压器的 buck。
LLC:LLC 也有很多变体,但优势很明确——零电压开通、零电流关断,效率很高;高频带来高密度。但由于是软开关特性,在这类应用里通常做成不稳压的变换器。它基于变压器,所以一般是不稳压的;效率很高,密度很高;想怎么扩展都行,改变压器即可。它会有点复杂——那些集成磁件的设计里门道很多,变压器设计是高效的关键。
飞电容类电路,比如现在很流行的混合开关电容:它可以是模块,也可以芯片化;不基于变压器,不是高频变压器方案。它可以半稳压——能降压,但不擅长升压,这跟飞电容的固有特性有关。它效率高:跑开关电容电路时,用那个技巧去降低电感上的伏秒,就不必靠提高频率硬扛。但它的可扩展性不强——它天生是 4:1 的降压比,要走到 50 转 6 就得多花些变化。而且复杂度高:有飞电容就要做均压,有很多浮地开关,这类挑战让设计更复杂。
最后,为什么不用最老实的 buck? 我们在最后一级就用它。buck 很简单、很直接、成本很低,没有 IP 方面的顾虑,而且完全稳压。我会说它效率中等或偏低、复杂度中等或偏低。但这是有原因的:用耦合电感、用 GaN 器件可以把效率提上去,可那就增加了复杂度——有 GaN 器件、有耦合电感,就不再简单直接了。所以它效率和功率密度都偏低,但它非常容易做多相,可扩展性极好。
所以在 50 V 这一级,我有很多权衡、很多选择,可以把你送到任何想要的电压。
So, topologies. How do you do this? Andy talked about the bricks in the previous talk. At 50 volts, we've been doing this a long time. We've been doing 50-volt brick converters for 30-plus years. So, you got full bridges, you got LLCs, you got hybrid switched capacitor, you got buck converters. There's a lot of different ways to get this 50 volt to 12, 50 volt to 6. And you can see they all have different pros and cons. Your full bridge: it's transformer-based. That generally suits it towards a module. You need a lot of layers to get your transformer losses down. It's a PWM controller. It's really easy to control, so regulation's not a problem. You fully regulate your output voltage, but it's got medium efficiency, medium power density. It works well at 12 V, it works well at 6 V because you can just change your transformer ratio in the design, and it's not that complex. It's a transformer-based buck converter. You got the LLC. There's lots of variants to these topologies as well, but the LLC has clear benefits. It's ZVS, ZCS, very high efficiency, high frequency gives it high density. But because of its soft-switching nature, generally in these types of applications you're going to run as an unregulated converter. It's transformer-based, so again, generally unregulated. It's going to have really high efficiency, really high density. Again, you can scale it any way you want, just change your transformer. And it's going to be somewhat complex. There's a lot that goes into those integrated magnetic designs. That transformer design's key to that high efficiency. And then we've got flying-capacitor-based circuits, like a hybrid switched capacitor, which is a popular one today. It can be module, it can be chip-down. It's not transformer-based, it's not a high-frequency transformer-based design. It can be semi-regulated. It can step down, but it doesn't like to boost, and that has to do with the inherent flying-capacitor nature. It's got high efficiency. When you run a switched-capacitor circuit, you use that trick to reduce the volt-second on your inductor, so you don't have to use high frequency. You can avoid using brute force. It's not as scalable. This is a natural 4:1 step down; it takes a little bit more variation to get to the 50 to 6. And it's got high complexity. You have flying capacitors, you have to have balance, you have a lot of floating switches. Challenges like that make it more complex. And then, why not the good old-fashioned buck? We use it at the last stage. Buck's very simple, very straightforward, very low cost. No IP concerns or anything of that nature. Fully regulated. I'll call it medium or low efficiency and medium or low complexity. But that's because you can increase the efficiency when you use things like coupled inductors, when you use things like GaN power devices — but then that adds to the complexity. You have a GaN device, you have a coupled inductor; those aren't as simple and straightforward. So it has a lower efficiency and a lower power density, but it's very easy to multi-phase. It's very scalable. So, I've got a lot of trade-offs, a lot of options at 50 volts to get you down to whatever voltage you want.
小结 50 V 这一级的四种拓扑没有「最优」,只有「配哪种架构」:全桥要稳压、LLC 要效率、混合开关电容要固定变比、Buck 要便宜和可扩展。
12 800 V:只剩堆叠 LLC
那么在 800 V 呢?
看 800 V,它要求——这里我改个说法,既然我们已经决定不叫它 HVDC 了。不过当你在一家做 3 V、5 V 工艺的公司里,800 V 对我们来说就是 HVDC,就是高压。
但在 800 V 下,它需要隔离,需要加强绝缘,所以爬电距离和电气间隙都要加大,而且软开关是必须的。你不会在 800 V 上做硬开关 buck,效率根本不够。同时你还需要大电流整流。
所以我们现在看到的,是各种 LLC 的变体——主要是堆叠 LLC,原边用 GaN,副边用 GaN 或 SiC。
另外,这套幻灯片提交之后,接下来几年随着这些系统落地,你们肯定会看到更多拓扑。右边会越来越像左边。但目前,这就是拿到所需效率和密度的通用做法。
So, where are we at 800? When you look at 800, it requires — I'll change this now that we've decided we're not going to call this HVDC. When you're in a company that makes three and five volt type processes, 800 is HVDC to us. It's high voltage. But at 800 volts, it requires isolation. It requires reinforced insulation. So, we have increased clearances, and soft switching is a must. You're not going to have a hard-switching buck converter at 800 volts; it's just not going to be efficient enough. And you're going to have high-current rectifiers. So, what we see right now is variants of the LLC. A lot of it's the stacked LLC with GaN primary and GaN or SiC secondaries. And then, since I've submitted these slides, over the next couple years as these systems come into fruition, you're going to see a lot more topologies. The right will start to look more like the left. Right now, this is the general approach to get the efficiency and to get the density needed.
小结 到了 800 V,拓扑选择反而变少:隔离、加强绝缘、软开关三条硬约束一卡,能上场的只剩堆叠 LLC——左边那四种拓扑的自由度,在右边并不存在。
第五部分 两块板子与保护
13 1 kW 与 10 kW:两块参考设计
那么它长什么样?
左边是我们做的 50 V 转 6 V LLC 参考设计:单模块能出大约 1 kW,满载效率 96% 到 97%,功率密度大约每立方英寸 2000 W。你可以看到它非常小、非常密——大约 40 乘 20 毫米。
从设计上看相当直接:一个原边,用 80 V 或 100 V 的氮化镓或硅器件;一颗 100 V 半桥驱动,我们做自举;60 V 以下全部是非隔离的,所以这里全是非隔离的。然后有一颗非常非常小的同步整流驱动,驱动大量低压 MOSFET,配一颗矩阵变压器。背面是数字控制器。
所以从设计角度,它挺简单。
到了高压这一侧,规模就上去了,设计也更有挑战。现在我们在 10 kW 这个量级。
当你必须加上这些间距、这些爬电距离、这些电气间隙,就没有多少空间再去堆一堆原边了;原边 FET 本身也大得多。所以它大得多,而且这是串联输入、并联输出的做法。
左边是 650 V 的 GaN 器件,我们把它们堆起来。红色高亮的那块是我们的高压爬电与间隙挖空区。
底部是一大堆遥测、一大堆隔离、一大堆偏置电源——要做保护、要做驱动,需要的东西很多,比简单的 50 V 设计复杂得多。同样还有数字控制器。
从功率角度看两者很像:都是 6 V 输出,但电流高得多,模块大得多,有一大堆并联输出的矩阵变压器,还有很多大电流母排去驱动这些同步整流器。
所以这是一个复杂得多的设计,复杂度高得多,需要的半导体也多得多。
So, what does it look like? Over on the left, this is a 50-V to 6-V LLC reference design we did. We can get about a kilowatt out of it, around 96-97% efficiency at full load, around 2,000 W per cubic inch. And you can see it's very small, very dense — roughly 40 by 20 mm. It's pretty straightforward. I have a primary side. I have 80- or 100-V gallium nitride or silicon devices. I have a 100-V half-bridge driver. We bootstrap it. Everything's non-isolated below 60 V. So, everything's non-isolated here. We've got a synchronous rectifier driver that's very, very small, drives a large number of low-voltage MOSFETs, with a matrix transformer. And then we have a digital controller on back. So, it's pretty simple from a design perspective. When we get to the higher voltage, this is where it becomes a bigger scale and a more challenging design. We're up around 10 kW now. When you look at the fact that we have to add all this spacing, all of this creepage, all of this clearance, we don't have a lot of room to add a whole bunch of primaries. The primary-side FETs get much larger, too. So, it's much larger, and this is a series-input, parallel-output type approach. On the left we have 650-V GaN devices, and we stack those. And you can see highlighted in red is our high-voltage creepage and clearance cutout. And on the bottom we got a whole lot of telemetry, a whole lot of isolation, and a whole lot of bias power. It takes a lot to protect, to drive — it's a lot more complex than a simple 50-V design. And again, you got the digital controller. And from the power perspective it looks pretty similar. It's 6-V out for both cases, but it's a lot higher current. It's a lot bigger module, with a lot of parallel output matrix transformers, a lot of high-current bus bars that are driving these synchronous rectifiers. So, it's a lot more complex design, a lot more complexity to it, a lot more semiconductors required.
小结 两块板输出都是 6 V、密度都是 2000 W/in³,但一块 1 kW、一块 10 kW——十倍功率不是靠放大,是靠八颗矩阵变压器并联、650 V 器件堆叠和一圈隔离器件换来的。
14 保护:从单边到双边
保护。
先说热插拔。50 V 相当直接:单边保护,一颗 80 V 或 100 V 的 FET。这一块我们已经做得不错了——你可以用两颗:一颗是大 SOA 的 FET 扛浪涌,另一颗是低导通电阻的 FET 在稳态时用,把总损耗降下来。但本质上就是单边保护、80 到 100 V 的 FET、没有隔离屏障。
到 800 V,这就复杂多了。双边保护——这也是我后面「呼吁」要讲的地方。一般要六颗 FET,高低边的热插拔要协同;我们集成了偏置电源,也集成了用于遥测和控制的数字隔离器。
最终它是能工作的:短路保护依然可以做得很漂亮。但同样,它不像低压那么简单。要支撑这种高功率、高压的保护,还需要新的、更好的 IC。
Protection. When we look at hot swap, 50 V is pretty straightforward. We've got single-side protection. You have an 80- or 100-V FET. In this case, we've gotten pretty good: you can have two FETs. You can have one that'll handle the inrush, a large SOA FET, and then you can have some low on-resistance FETs while it's cruising along, to reduce your overall losses. But I have single-side protection, 80-100 V FETs, no isolation barriers. When I look at 800 V, this is a lot more complicated. I have double-sided protection. And this is where this will come to my call to action. We have double-sided protection, generally six FETs. You got to coordinate the high and low-side hot swaps. We integrate a bias supply, we integrate digital isolators for the telemetry and control. And ultimately it could work: you can still have a very good short circuit, good protection. But again, it's not as simple as it would be at low voltage. It's going to take some new, better ICs to enable these high-power, high-voltage protection.
小结 保护这一页是整场最容易被低估的成本:50 V 一颗 FET 就能挡住的事,到了 800 V 要六颗、要双边协同、要隔离偏置——而短路保护仍要在 1 µs 以内完成。
第六部分 结论
15 总结与呼吁
总结,也是呼吁。
我们知道 HVDC 正在支撑下一代服务器的功率需求。最好的实现路径并不清晰,但在我看来,垂直送电会赢——最后一公里离处理器越近,它就越重要。
GaN 和 SiC 会变得更加重要。走向高压高密度,宽禁带是关键的使能技术之一。
但还有一批无名英雄:需要大量的保护,而且必须是隔离的——加强绝缘、大量偏置电源、大量栅极驱动、大量遥测。
所以我的呼吁是:这里由 OCP 驱动的标准,可以消除定制工程、缩短供应商的上市时间。
举几个例子。爬电距离和电气间隙的安全规范我们都清楚,但我可以告诉你,跟这个圈子里的不同客户聊,我们每次拿到的数字都不一样。而每加一毫米、减一毫米就要重新开一颗料,工作量极大,真的把节奏拖慢。
所以当我们走向这些 OCP 驱动的标准,希望能缩短上市时间,也给我们一个清晰的说法:到底要提供什么。DC-DC 变换器的尺寸与需求也是同理,保护要求也一样——到底需要单边还是双边?两线还是三线?诸如此类。
这就是我的呼吁。谢谢大家。
To summarize and a call to action. So, we know HVDC is enabling the next generation of servers. The best way to get there is not clear, but from my perspective, vertical power delivery is going to be the winner. Getting that last mile, the closer you get to the processor, the more important it is. GaN and SiC are going to be even more important. Wide band gap is going to be one of the key enablers as we go to this high voltage and high density. But the unsung heroes: it's going to take a lot of protection, and it's got to be isolated. You got to be reinforced insulation, a lot of bias supplies, a lot of gate drives, a lot of telemetries. So, the call to action: OCP-driven standards here is going to eliminate the custom engineering and shorten the supplier time to market. And I'll give some examples. We all know the specs, the safety specs for creepage and clearances, but I can tell you when we talk to the various customers in this place, we have a different number every time. And spinning a new part every single time we need to add a millimeter or take away a millimeter — that takes a lot of effort. It really slows things down. So, as we move to these OCP-driven standards, hopefully it can shorten our time to market and really give us good clear guidance on what we need to provide here. Same goes with the DC-DC converter dimensions and needs, as well as the protection requirements. Do I need a single side? Do we have two wire? Do we have three wire? Those types of things. So, that's my call to action, and I'd like to thank everybody.
小结 总结里最硬的一句不是「VPD 会赢」,而是「爬电距离每家客户给的数都不一样」——标准缺位,正在把功率器件开发变成一次性的定制工程。
16 致谢
Thank You! Any questions?:OCP Global Summit 2026
很遗憾,我们没有时间提问了——除非有非常简短的问题。
Well, unfortunately, we don't have time for questions unless there's a quick question.
小结 25 分钟塞进五种架构、四种拓扑、两块参考设计和一套保护方案,没有留问答时间,内容密度可见一斑。
(转自公众号:一超一世界)